It is known that materials or goods in granular or powder form are marketed in substantially parallelepiped-shaped bags, which are manufactured in this shape and provided at either piece of one of the shorter sides of the top end of the bag with an opening having closing lips and constituting a valve, adapted to receive the charging nozzle of a sack-filling machine, said opening closing automatically as a result of the thrust exerted by the material within the bag upon the valve inner lip when said material has filled up the bag. Such bags will hereinafter be referred to as "valved bags".
Known bag-filling machines effect in a completely automatic cycle both the filling of the bag through the inserted charging nozzle and the removal of the bag after filling.
However, the attendance of an operator is required to pick up empty bags from a stack thereof and place them one at a time over the charging nozzle, meanwhile discarding any defective bags.
The valved bags are in fact, also manufactured on completely automatic machines which cut a web of paper or other sheet material of which the bag is to be manufactured, and fold it suitably in order to form the valve at one end, whereafter the edges are glued leaving the valve free.
These being high-production machines, minor defects are inevitable during the various stages of bag manufacture, particularly during the glueing stage and therefore it is common to find defective bags, mainly in the zone of the valve, which could appear glued or be difficult to open or have permanent wrinkles, and therefore during the working stage, effected at a predetermined rate, the bags must be discarded. Such a labour cost for an apparently simple operation raised the problem of mechanising the operation of lifting the bags for insertion on to the charging nozzle.
Recently devices have become known in the art which pick up one bag at a time from a stack or roll, open out the valve lips and thereafter push the bag on to the charging nozzle of a bag-filling machine, withdrawing thereafter to repeat the cycle.
Besides the fact that said devices are extremely complicated, none of them can discard the defective or inoperative bags, as the operator does, so that when they handle a bag having one of the above-mentioned defects (glued or badly manufactured valve, or wrinkles, which are rather usual events as it is well known to persons skilled in the art) they nonetheless carry out the operation causing the bag-filling machine to jam or even to break down, spreading the material all over and requiring therefore the operator's attendance to discard the defective bag and resume the operative cycle.
It is an object of the invention to provide an apparatus for automatic insertion of a valved bag, which besides collecting the bags from the pile or whatsoever packaging arrangement of the same and inserting the valve on the charging nozzle, checks the bag efficiency and in case of a defective bag discards it automatically without any external intervention.